Electric arc



June 18, 1940. N. PIIERRON ET AL ELECTRIC ARC Filed Oct. 30, 1957 2Sheets-Sheet 1 l N Vi N E S N l Rarren .FIer re W j HIHIH lxllllll June1940- N. PIERRON ET AL 5, 7

ELECTRIC ARC Neal Rerrb Pmrre Avbrg INVENToZ Patented June 18, 1940UNITED STATES PATENT OFFICE France, assignors to Pathe Cinema, AnclensEtablissements Pathe Freres, Paris, France, a

company of France Application October 30, 1937, Serial No. 111,888 InFrance July 19, 1937 6 Claims.

It is known that the brilliancy of the crater of the positive carbon ofa "high intensity elec-- tric arc is a function of the current densityin the carbon (number of amperes per unit of sec- 5 tion). This functionis not linear-4n fact, the brilliancy increases at a much higher ratethan the current density, and when this variation is graphicallyrepresented, the result will be a curve, termed brilliancy-densitycharacteristic, the slope of which increases very rapidly.

On the other hand, the rate of consumption of a given carbon dependsexclusively upon the energy W consumed in the arc. This rate ofconsumption also increases much more rapidly than 15 W, and in this caseas before, the graphic representation of the phenomenon leads to acurve,

termed consumption-energy characteristic. the

slope of which also increases very rapidly.

It will follow from the preceding considera- 20 tions that in order toobtain in an are a very great brilliancy of the crater, which is the object to be attained, it is desirable to use for the positive carbon asgreat a value of current as possible (this being however compatible withthe stability of the arc and the optical arrangement of the lantern),but this will cause a very rapid consumption of the carbon. as theenergy taken up by the arc increases with the current density.

The points which represent an operation with good efficiency are thuslocated, on the characteristic curves of the arc, in regions in whichthe slope is very rapid, but at these points, the least variation of theenergy taken up by the arc is at once manifested by a marked variationin the rate of consumption.

One object of the present invention is to provide a method forregulating the electrodes producing an electric arc adapted forlighting, heating, or the like. in which each of the two electrodecarriers is actuated independently from one another by a common electricmotor operating at a constant speed. by the use of two separatetransmission devices the ratios of which can be adjusted.

Experience as well as theory (as will be further disclosed) show thatfor constant and determined feeding speeds of the electrodes, theconsumption of these electrodes will afford automatically-for a givencurrent-a constant spacing and'hence a constant useful efiect, whetherthis effect is an intensity'of light or a quantity of generated heat. I

In order ,to increase this useful effect, which thus will correspond toa new value of the current, it is simply necessary to increase the speed(Cl. PIG-51) at which the two electrodes are fed. When the currentincreases, the consumption will also increase, and after a short time,the arc will be again stabilized at the spacing which corresponds to thenew value of the current desired.

The invention further consists of an arc apparatus, (lamp, heatingapparatus) for carrying out the aforesaid method of regulation.

The said apparatus comprises an electric motor operating at a constantspeed,-a cam or like member which is rotated by the said motor throughthe medium of a speed-reducing mechanism, two free-wheel mechanisms thedriving elements of which are given an alternating movement, in onedirection by the said cam, and in the other direction by elasticreaction devices, whilst the two driven elements are each connected toone of the respective electrodes by a suitable transmission, and twostops which are adapted to be adjusted independently from one anotherand are each combined with the driving element of one of the twofree-wheel mechanisms, in such a manner as to regulate the amplitude ofits oscillations by adjusting the extent of the return movement.

Further features of the said invention will be set forth in thefollowing description.

In the accompanying drawings, which are given solely by way of example:i

Fig. l is a diagram relating to the method.

Fig. 2 is a diagrammatic longitudinal section of an arc lamp.

Fig. 3 is an enlarged cross-section on the line 3-3 of Fig. 2.

Fig. 4 is a diagrammatic view of an electrooptical device for theautomatic regulation of the position of the negative electrode.

In Fig. 1 is shown a positive electrode I consisting of a carbon inwhich a crater l is formed. and a coaxial negative electrode 2 which hasa smaller diameter and ends in a tip 2 According to the invention, theelectrodes I and 2 are given contrary displacements, in the directionsof the arrows f and f and the speeds V and V of the said electrodes aresuch that they will compensate for the linear consumption U and Ucorresponding to the electrical conditions for a given distance ebetween the end planes AA and BB of the two electrodes.

In these conditions, if the two electrodes ar moved apart, this willcause a reduction in the consumption of energy W, but this will greatlyreduce the linear consumption or rates of consumption U and U of theelectrodes. On the contrary, if the electrodes are brought nearertogether, W will increase, and the rate of consumption will increase.

It is now supposed that the feeding movement of the electrode 2 exactlycompensates for its consumption so that the said electrode will bestationary in space. Electrode I is fed at the speed V and itsconsumption takes place at a speed U corresponding to a distance 6.

If the end of the positive carbon I is brought in the plane A. A, W willincrease. The rate of consumption of the carbon will increase morerapidly than W, and will reach a value V. As the speed V is at this timeless than U. the crater of the carbon I will tend to recede until thedistance e again becomes equal to e, thus affording a consumption Wcorresponding to a consumption U equal to V The conditions are quite thesame when the end of electrode I is brought in the plane A". A". and itis thus evident that the arc will always stabilize when U =V and this.for a given current. will afford a given distance 6 and a consumption Wto which corresponds a well-defined useful effect.

It will be thus observed that a self-regulation of the distance betweenthe carbons takes place, provided that the speed of translation V isconstant if it is not desired to introduce other factors which. beingindependent of the characteristic of consumption. would cause troubleand would entirely transform the principle of selfregulation.

It should be noted that it is advantageous to operate in the part of theconsumption-energy characteristic having a great slope, so that toslight variations of current (i. e. to slight variations of the distancee) will correspond great variations in the speed of consumption of theelectrodes. In this manner, the sensitiveness of the adjustment isgreatly increased, as the rapid variations of the speed of consumptionwill afford a very rapid return to the normal distance 6, after adisturbance. for instance due to the nature of one of the electrodes,has caused a variation of said distance.

In the preceding considerations; it has been supposed that the end ofthe negative carbon 2 has remained in the plane BB, and that the rate ofconsumption W of the negative carbon was exactly equal to the rate ofthe feed V Now. the characteristic curve of the consumption of thenegative carbon in function of the power W has not the same form as thecharacteristic curve of the consumption of the positive carbon. Theslope of the curve of the consumption of the negative carbon in functionof W increases but little with the increase of W contrarily to the slopeof the curve of the consumption of the positive carbon. In consequence,admitting that the rate of consumption W of the negative carbon 2 isless than the rate of feed V of this carbon, the negative carbon willmove towards the positive carbon. When the distance between the carbonsdecreases, W will increase. But the positive carbon, the rate ofconsumption of which is considerable, will be consumed more rapidly, andits crater moves back, so that the gap of the arc remains constant. Thusthere is observed a movement of the two carbons in one direction or theother according as the rate of consumption U of the negative carbon islarger or smaller than its feeding rate V.

In the arc lamps used for the projection of motion picture films, as thecrater I of the positive carbon I should be located at the focus of anoptical system, it is evident that a movement of the carbons will causea reduction of the optic l efliciency of the apparatus. Fortunately,experience shows that the very slow consumption of the negative carbon 2permits a relatively exact regulation of its feeding speed.

By way of example, an arc can be made to operate with the adjustmentaccording to the invention for 30 or 40 minutes, without being obligedto make any manual correction. Inasmuch as in a motion picture plant, anarc must operate for 20 to 25 minutes at the maximum without stopping,it may be considered that the are which is regulated by supposing thenegative electrode stationary, does not require any manual correction.

Figs. 2 and 3 show by way of example an arc lamp according to theinvention.

The said lamp comprises in the known manner, in the interior of a casing3, a mirror 4 adapted to reflect, through an opening 5, a strong beam oflight issuing from the are which is formed between the crater I oi! apositive carbon I and the point 2 of a negative carbon 2. The crater ofthe positive carbon I must be maintained at the focus of the mirror I,in spite of the consumption of this carbon, and the negative carbon 2must be maintained at a given distance e from the positive carbon I,which distance e depends, as above stated, upon the current I and thedesired power W, and also upon the nature and the crosssections of theelectrodes I and 2.

The positive carbon I, which rests at the front part upon a supportingfork 5, is clamped, at the rear, by means of a screw 6 operated by alever I, in a carbon clamp 8 mounted on a bracket 9 which is pivotedabout an axle I Ii on a support I I. Support II to which is connected awire I2 for the supply 01 current, is secured, with interposition of aplate and insulating tubes, to a carriage I! which, at the outside ofthe casing 3, forms a nut upon a'driving screw it The carriage I3 can beuncoupled from the said screw by known means, not shown.

Said screw I 4 may be operated by hand from the outside of the casing 3by means of a shaft I 5 and bevel gearing I8, in view of regulating thecarbon I by hand.

To provide for the automatic feed in the direction of the arrow 1 at thespeed V corresponding to a rate of consumption U the screw I4 extends asfar as a case I! (Figs. 2 and 3) which is secured to the rear side ofthe casing 3 and contains the driving mechanism.

The said mechanism comprises an electric motor I8 operating at constantspeed, and actuating, for example through a torque-limiting device IS,the driving shaft of a speed-reducing device 20. On the driven shaft 2|of the said speed-reducing device is mounted an eccentric cam 22, whichacts at each revolution to drive back, in succession, two rollers 23 and24.

Roller 23 is mounted on a push-rod 25 which is slidable in a tubularmember 26 carried by the case II. The said push-rod acts upon an arm 28which is integral with a sleeve 29 which is concentric with the end ofscrew I4 actuating the carriage I! of positive carbon I. Sleeve 29,which is urged in the direction of the arrow 1 (Fig. 3) by a spring III,is connected, as to rotation, to the screw I4 by av free-wheel mechanismof any known type comprising balls and inclines or the like, so that thesleeve 29 will actuate the screw I4 in the proper direction to move thepositive carbon I towards the negative carbon 2 when the said sleeverotates in the contrary direction to the a row by the action of thepush-piece 25. The return or the said sleeve under the two carbons I, 2.

action of the spring 30 has no effect upon the screw i4.

011 the same side as the push-piece 28, is mounted an adjustable stop32' formed by the end of a screw 33 which is provided with an operatinghead and can be screwed more or less into the wall of the case II. Thesaid stop limits the return stroke of the sleeve 28 and the arm 28 underthe action of the spring 30. As the extent of the working stroke isfixed and is determined by the maximum forward movement of the pushpiece25 under the action of the cam 22, it will be noted that the amplitudeof the successive oscillations of the said sleeve and hence, of thesuccessive rotations of the screw I 4 in the same direction, will dependupon the position of the stop 32. By adjusting this stop, it is an easymatter to regulate the forward speed V of the positive carbon I, thespeed of the motor l8 remaining constant. and such that it is capable.taking account of the speed-reducing device 28 and the cam 22. to impartto the carbon I the greatest speed that can be required.

The other roller 24, which is acted upon by the cam at each rotation, ismounted on the end of an arm 35 which is urged by a spring 36 and isintegral with a sleeve 31 which actuates a worm 39 by means of afree-wheel 38 when it oscillates in the direction of the arrow 1. Worm33 meshes with a worm-wheel 40. Said worm-wheel is loosely mounted upona transverse shaft 43 but is adapted. to drive said shaft in rotationthrough a disc 41 which is urged in frictionalengagement with one of theend faces of the worm-wheel 40 by a spring 42 which also provides forrotation of shaft 43 with disc 4!.

A screw-stop 44 the position of which is adcessive rotations, all ofwhich are in the same direction, which are imparted to the worm-wheel 40and hence to the shaft 43, owing to the friction coupling 4|, 42. Thesaid shaft 43 can also be actuated by hand, by means of a knob 46. In

this case, the worm 39 is held stationary, and the worm-wheel 40 willrotate about the shaft 43, owing to the friction-coupling 4|, 42. To theshaft 43 is keyed a pinion 41 consisting of insulating material. 46movable in guides 49 mounted upon a supporting member 50, which issecured to the case i! by screws 5| provided with washers and insulatingbushings, being thus insulatedagainst bodycontact. The rack 48 isconnected by an axle IN to the lower jaw 52 of the negative carbonholder. The other jaw 53 is pivoted to the jaw 52 by a pivot-axle 54,and the negative carbon is clamped between the two jaws by a screw 56.

The negative current is supplied to the electrode 2 by a conductor 66.

It is observed that the feed of the negative carbon 2 in the directionof the arrow f can be obtained from the shaft 43, either by hand bymeans of the knob 46, or automatically. from the motor I8, by means ofthe cam 22, the arm 35, the free-wheel 38, the worm 38 and the wormwheel48, the feeding speed V being regulated by the stop-screw 44.

' The negative carbon 2 rests upon a supporting fork 51 which isadjustable both laterally and vertically by screws 58.

The apparatus is completed, in the known manner, by means for indicatingthe positions of the The said pinion engages a rack Such means, notshown, consist of two. indicating marks which are located at the outsideof the casing 3 and upon which an optical device projects through anopening 68 in the said casing the image of the incandescent ends I and2' of the two carbons.

The operation is as follows. The operator is aware that he is to workwith a given current I, taking due account of the nature and the qualityof the carbons in use. The current being supplied, with the electrodesl-2 in any position, the operator handles the hand control knobs inorder to bring the ends i -2 of these electrodes adjacent the tworespective indicating marks, then by acting upon the stops 32 and 44 here ulates the automatic feeding speeds V and W of the electrodes in suchway that these speeds will correspond to the rate of consumption U and Wfor the given operating conditions (current I, distance e of theelectrodes, power consumed W). When the adjustment has been made andcorrected if necessary, the distance e between the electrodes |2 isautomatically maintained constant as above described, and since theconsumption of the negative carbon 2 may be considered as practicallyconstant for a relatively long operating period, the two carbons l and2, the distance e of which is now constant, remain practically fixed inspace, and the crater I of the positive carbon I remains at the focus ofthe mirror.

However, in the case in which an arc providsd with the aforesaidregulating devices is required to operate in an inaccessible place andfor a very long time, it may be provided with means forautomaticallyfixing in space the point 2 of the negative carbon 2.

Such means may comprise.,as shown in Fig. 4, a lens; 59 which receivesthe light from the incandescent point 2 of the negative carbon 2.

justable screen 60 which is slotted at 60, and

in the rear of which is located a photo-electric cell 6|.

This cell controls a relay 6| adapted to open and close the circuit ofan electromagnet 62 which acts upon a pawl 63 engaging a toothlng 64rovided on the sleeve 31 which is secured to the lever 35.

The regulation consists in giving to the feeding speed V of the negativecarbon 2, a value which exceeds the rate of consumption U In 'theseconditions, when the image of the negative point 2 is no longer oppositethe slot 60 in the screen 60, the photo-electric cellfil actuates therelay Bl which closes the circuit of the electromagnet 62, and thus thesoft iron pawl 63 is attracted by the electromagnet and it will engagethe toothlng of the sleeve 31 when this latter is at the end of itsworking stroke. The sleeve 31 is thus held stationary, and under theaction of its spring 36 it can only oscillate, at the maximum, throughan angle corresponding to the distance between two teeth of the toothlng64. 'As the amplitude of oscillation of the lever 35 has thusdiminished, the rate of feed of the negative carbon has also diminished.Owing to the consumption of the carbon 2, the point 2 will moverearwardly, and its image will again coincide with the slot BM of thescreen 60 and will thus act again upon the cell 6|. The relay lil thenopens the circuit of the electromagnet 62, and the pawl 63 drops down,thus releasing the sleeve 31 and the amplitude of the oscillations oflever 35 will again take their maxi- ,The image of this point isprojected upon an ad- 7 mum value corresponding to the initialadjustment.

Thus the mechanism will act the more frequently as the rate of feed ofthe negative carbon 2 is greater in proportion to the rate ofconsumption of the carbon.

As a principle, the distance e of the carbons 1-2 being constant, itwill be understood that if the position of the negative carbon 2 isfixed in space, the position of the positive carbon l is also fixed.

Obviously, the said invention is not limited to the embodiments hereindescribed and represented, which are given solely by way of example.

Having now described our invention what we claim as new and desire tosecure by Letters Patent is:

1. In an electric arc apparatus, the combina tion with the twoelectrode-holders of a motor rotating at a constant speed duringconstant time units, and for each electrode-holder an independent speedreducing gears actuated by said motor and feeding means adapted todisplace said electrode-holder towards the other electrode-holder, andtransmission means between said motor and each feeding means, thetransmission ratio of each transmission means being independentlyadjustable, whereby each electrode-holder is given a regular andconstant displacement during each time unit.

2. In an electric arc apparatus, the combination with the twoelectrode-holders of a motor rotating at a constant speed duringconstant time units, and transmission means comprising independently foreach electrode-holder a pivoted member adapted to oscillate between twoadjustable extreme positions and actuated by said motor, a rotatableshaft and a one way clutch between said pivoted member and said shaftadapted to rotate said shaft in one direction, and feeding means betweeneach electrode-holder and the corresponding shaft actuated by said shaftto displace said electrode-holder towards the other electrode-holder,whereby each electrode-holder is given a regular and constantdisplacement during each time unit.

3. In an electric arc apparatus, the combination with the two electrodeholders, of a motor rotating at a constant speed, a cam rotated by saidmotor, and between said cam and each of said electrode holderstransmission means comprising a free wheel mechanism including a drivingmember and a driven member, spring means,

said driving member effecting a working stroke under the action of saidcam and against the action of said spring means and a return strokeunder the action of said spring means, said driven member rotating withsaid driving member during said working stroke and being released fromsaid driving member during said return stroke, stop means limiting thereturn stroke of said driving member whereby the amplitude of theworking stroke is also limited, and means provided between said drivenmember and the corresponding electrode-holder to feed the electrode whensaid driven member rotates.

4. In an electric arc apparatus, the combination with the two electrodeholders, of a motor rotating at a constant speed, a cam rotated by saidmotor, and between said cam and each of said electrode holderstransmission means comprising a free wheel mechanism including a drivingmember and a driven member, spring means, said driving member efiectinga working stroke under the action of said cam and against the action ofsaid spring means and a return stroke under the action of said springmeans, said driven member rotating with said driving member during saidworking stroke and being released from said driving member during saidreturn stroke, adjustable stop means limiting the return stroke of saiddriving member whereby the amplitude of the working stroke is alsolimited, and means provided between said driven member and thecorresponding electrode-holder to feed the electrode when said drivenmember rotates.

5. In an electric arc apparatus, the combination with the two electrodeholders, of a motor rctating at a constant speed, a cam rotated by saidmotor, and between said cam and each of said electrode holderstransmission means comprising a free wheel mechanism including a drivingmember and a driven member, spring means, said driving member effectinga working stroke under the action of said cam and against the action ofsaid spring means and a return stroke under the action of said springmeans, said driven member rotating with said driving member during saidworking stroke and being released from said driving member during saidreturn stroke, adjustable stop means limiting the return stroke of saiddriving member whereby the amplitude of the working stroke is alsolimited, and means provided between said driven member and thecorresponding electrode-holder to feed the electrode when said drivenmember rotates, a photo-electric cell positioned to receive a flux oflight from the incandescent end of the negative electrode, a relaysupplied with current by said photo-electric cell, a screen interceptingsaid flux of light when the position in space of said incandescent endchanges, electromagnetic means controlled by said relay so that thesupply circuit of said electromagnetic means is closed when said flux oflight is intercepted as a result from a too rapid feeding movement ofsaid incandescent end, locking means holding against rotation thedriving member of the free-wheel mechanism controlling the negativeelectrode when said electromagnetic means are supplied with current,whereby, when the one of said stop means corresponding to said negativeelectrode is adjusted for a feeding speed which exceeds the rate ofconsumption of the negative electrode, said incandescent end ismaintained in a fixed position in space.

6. A combination as claimed in'claim 5, in which said locking meanscomprise a pawl attracted by said electromagnetic means and a toothingprovided on the driving member controlling the negative electrode, saidpawl engaging said toothing when attracted by said electromagnetic meansand to hold said last mentioned driving member against rotation.

NOEL PIERRON. PIERRE AUBRY.

